Thin-film transistor array and method of fabricating the same

Abstract

A thin-film transistor array includes a substrate, an electrically conductive portion, and a metal layer. The electrically conductive portion is made of one of indium tin oxide, indium oxide, and tin oxide. The electrically conductive portion and the metal layer are formed on a common surface of the substrate. The metal layer includes a first layer and a second layer. The first layer is made of one of aluminum and an aluminum alloy. The second layer extends on the first layer and is made of metal having an oxidization potential nobler than a reduction potential of said one of indium tin oxide, indium oxide, and tin oxide in alkaline aqueous solution.

What is claimed is:  
     
         1 . A thin-film transistor array comprising: 
 a substrate;    an electrically conductive portion made of one of indium tin oxide, indium oxide, and tin oxide; and    a metal layer;    wherein the electrically conductive portion and the metal layer are formed on a common surface of the substrate; the metal layer includes a first layer and a second layer; the first layer is made of one of aluminum and an aluminum alloy; and the second layer extends on the first layer and is made of metal having an oxidization potential nobler than a reduction potential of said one of indium tin oxide, indium oxide, and tin oxide in alkaline aqueous solution.    
     
     
         2 . The thin-film transistor array of    claim 1   , wherein the metal layer further includes a third layer for preventing diffusion, the third layer extending below the first layer.  
     
     
         3 . A method of fabricating a thin-film transistor array, comprising the steps of: 
 forming an electrically conductive portion on a substrate, the electrically conductive portion being made of one of indium tin oxide, indium oxide, and tin oxide;    processing the electrically conductive portion by photolithography;    sequentially forming first and second metal layers on the electrically conductive portion, the first metal layer being made of one of aluminum and an aluminum alloy, the second metal layer extending on the first metal layer and being made of metal having an oxidization potential nobler than a reduction potential of said one of indium tin oxide, indium oxide, and tin oxide in alkaline aqueous solution; and    processing the first and second metal layers by positive-type photolithography.    
     
     
         4 . The method of    claim 3   , further comprising the step of forming a third metal layer for preventing diffusion, the third metal layer extending below the first metal layer.  
     
     
         5 . A thin-film transistor device comprising: 
 a transparent electrode made of indium tin oxide; and    a thin-film transistor electrically connected to the transparent electrode and including a multilayer metal region;    wherein the multilayer metal region includes a first layer and a second layer; the first layer contains aluminum; and the second layer covers at least part of the first layer and is made of one of molybdenum, titanium, tungsten, tantalum, and an alloy containing at least two of molybdenum, titanium, tungsten, and tantalum.    
     
     
         6 . A method of fabricating a thin-film transistor device, comprising the steps of: 
 forming a transparent electrode made of indium tin oxide; and    forming a thin-film transistor electrically connected to the transparent electrode and including a multilayer metal region, the multilayer metal region including a first layer and a second layer, the second layer extending on the first layer;    wherein the transistor-forming step comprises: 
 forming a first metal film containing aluminum after the electrode-forming step;  
 superposing a second metal film on the first metal film, the second metal film being made of one of molybdenum, titanium, tungsten, tantalum, and an alloy containing at least two of molybdenum, titanium, tungsten, and tantalum; and  
 processing the first metal film and the second metal film into the first layer and the second layer respectively by positive-type photolithography.